1. Field of the Invention
The present invention relates to a semiconductor device having contact parts according to a self-alignment method and production method for the same.
2. Prior Art
The integration degree of semiconductor devices has increased in recent years while memory cells have been scaled down and, at the same time, it has become difficult to open contact holes between wires, by using solely a photoresist mask, without causing short circuiting from the wires. Therefore, a method called the self-alignment method is adopted as a method for opening contact holes without short circuiting the wires.
In the following, a structure of a conventional semiconductor device as well as its production method in the case that a self-alignment method is adopted are described in reference to FIG. 61.
As shown in FIG. 61 isolation regions 11 are selectively formed on the main surface of a semiconductor substrate 10. Then a silicon oxide film 1 is formed on the main surface of the semiconductor substrate 10 and the wiring is formed thereon. The wires have a polycrystal silicon film 2 and a silicide film 3.
On the wiring a nitride film (a hard mask film) 4 is formed. A silicon oxide film 5 is also formed on the side walls of the wires. At this time the oxidation rate of the silicide film 3 is faster than that of the polycrystal silicon film 2 and, therefore, the silicon oxide film 5 has a shape which locally projects to the side.
A nitride film 6 is formed so as to cover the silicon oxide film 5 and nitride film 4. A silicon oxide film 7 is formed so as to cover this nitride film 6 and an interlayer oxide film 8 is formed so as to cover the silicon oxide film 7.
Afterwards contact holes which reach to the main surface of the semiconductor substrate 10 are formed between the wires and conductive layers (plug parts) are formed within the contact holes.
In the above described prior art wherein a self-alignment method is adopted, however, a defective filling of the interlayer oxide film 8 can occur in the case that scaling down has further advanced so that the distance between wires becomes very short.
As for a primary cause of the defective filling of the interlayer oxide film 8, firstly, the fact that the upper edge corner part of the wires as shown in FIG. 61 are squared can be cited. Because of the existence of those squared parts the opening areas on the upper surface of the regions between the wires become smaller so as to cause the easy occurrence of a defective filling. The existence of the projecting parts on the side walls of the wires as shown in FIG. 61 can also be a primary cause of defective fillings. In addition, the steepness of the side of the wires can be a primary cause of defective fillings.
The occurrence of the defective fillings of the interlayer oxide film 8 as described above causes a void 9 between the wires as shown in FIG. 61. In the case that the void 9 has occurred in this way, a conductive layer is filled in, as well as into the void 9, when plug parts are formed within the contact holes in the latter process. Thereby, the contact parts 24 are connected to each other with the conductive layer which is filled in within the void 9 as shown in FIG. 62, which leads to the problem that the plug parts are short circuited with each other. Here, in FIG. 62, active regions are denoted as 22 and wires are denoted as 23.
The development of scaling down has been particularly remarkable in recent years and there is a tendency that the height of the wires have become larger in order to decrease the wiring resistance and, therefore, the situation of the above described problem is more and more prone to occur.
The present invention is provided to solve the above described problem. The purpose of the present invention is to prevent a short circuit between the plug parts due to defective fillings or the like of the interlayer insulation film between the wires.
A semiconductor device according to one aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with an insulation film interposed, a hard mask film on the wires, a nitride film having rounded upper edge corner parts covering the hard mask film, an interlayer insulation film covering the nitride film and plug parts formed within the interlayer insulation film. Here, in the present invention, the plug parts are referred to as conductive parts formed within the interlayer isolation film so as to connect conductive layers to each other. Accordingly, the plug parts according to the present invention may be formed as a part of wiring in one case and may be formed of a conductive material which is different from that of the wiring in another case.
By rounding the upper edge corner parts of the nitride film as described above, the opening areas of the upper surface of the regions between the wires can be increased in comparison to the case where the upper edge corner parts of the nitride film are not rounded. Thereby, defective fillings of the interlayer insulation film between the wires can be limited.
In the case that the width of the nitride film located on the above described hard mask film is denoted as L and the height from the bottom of the hard mask film to the top of the nitride film is denoted as H, it is preferable for the width a of the rounded part in the nitride film to be in the range of 0 less than a less than L/2 and for the height b of the rounded part to be in the range of 0 less than b less than H. Thereby, the opening areas of the regions between the wires can be effectively increased.
In addition, the hard mask film has, preferably, rounded upper edge corner parts. In this case the upper edge corner parts of the nitride film can be rounded so that the defective fillings of the interlayer insulation film between the wires can be limited.
In the case that the width of the hard mask film is denoted as L and the height is denoted as H it is preferable for the width a of the rounded upper edge corner parts in the hard mask film to be in the range of 0 less than a less than L/2 and for the height b of the rounded parts to be in the range of 0 less than b less than H. Thereby, the opening areas of the regions between the wires can be effectively increased.
A semiconductor device according to another aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with an insulation film interposed, a hard mask film on the wires, an oxide film formed on the side walls of the wires, a nitride film covering the hard mask film and the oxide film, an interlayer insulation film covering the nitride film and plug parts formed within the interlayer insulation film. Then the surface of the oxide film extends substantially in the direction perpendicular to the main surface of the semiconductor substrate without locally projecting to the side.
In this case, since the oxide film formed on the side walls of the wires does not protrude to the side, the defective fillings of the interlayer insulation film between the wires can be controlled in comparison to a prior art wherein the oxide film projects to the side.
The above described wires have a silicon film and a silicide film so that the side of the silicide film is located inward than the side of the silicon film. Then the shift amount of the side of the silicide film to the inner side of the wires from the side of the hard mask film is preferably xc2xd times or more and {fraction (3/2)} times or less as large as the thickness of the oxide film located on the side walls of the silicon film.
By properly adjusting the shift amount of the side of the silicide film in this way the surface of the oxide film can be prevented from locally projecting to the side so that the defective fillings of the interlayer insulation film between the wires can be limited.
A semiconductor device according to still another aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with an insulation film interposed, a hard mask film on the wires, a side wall insulation film extending from the side walls of the wires to the side walls of the hard mask film, a nitride film formed on the side wall insulation film, an interlayer insulation film covering the nitride film and plug parts formed within the interlayer insulation film.
By forming a side wall insulation film on the side walls of the wires as described above, it becomes possible to make gradual the slope of the side walls of regions located between the wires. Thereby, the defective fillings of the interlayer insulation film between the wires can be limited.
In the case that the width of the bottom of the above described side walls insulation film is denoted as a1 and the height of the side wall insulation film is denoted as b1, it is preferable for the value of b1/a1 to be larger than 2 and smaller than 15. Thereby, it becomes possible to make gradual the slope of the side walls of the regions located between the wires.
A semiconductor device according to yet another aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with a first insulation film interposed, a hard mask film on the wires, a nitride film covering the hard mask film, an interlayer isolation film covering the nitride film and having contact holes which reach the main surface, a second insulation film covering the side walls of the contact holes and plug parts formed within regions surrounded by the second isolation film.
By covering the side walls of the contact holes with the second insulation film in this way, even in the case that a void is formed in the interlayer insulation film and a conductive material for forming plug parts infiltrates inside the void, short circuiting between this conductive material and the plug parts can be prevented.
A semiconductor device according to yet another aspect of the present invention comprises a semiconductor substrate having a main surface, element isolation regions selectively formed in the semiconductor substrate, first and second wires which are formed on the main surface with an insulation film interposed and which extend in the element isolation regions, a first and second hard mask films on the first and the second wires, a nitride film covering the first and second hard mask films, an interlayer insulation film covering the nitride film, plug parts formed within the interlayer insulation film, first regions located on the isolation regions wherein the gap between the first and the second wires is relatively broad and second regions located on the isolation regions wherein the gap between the first and the second wires is relatively narrow.
By locally expanding or contracting the gap between the wires in this way, the following effects can be gained. In the case that the gap between the wires is locally expanded, the aspect ratio of the regions can be made smaller so that the defective fillings of the interlayer insulation film between the wires can be limited. On the other hand, in the case that the gap between the wires is locally small, the regions between the wires can be locally filled with the nitride film. Thereby, it becomes unnecessary to fill in the interlayer insulation film in the regions so that the defective fillings of the interlayer isolation film in the regions can be controlled.
In the case that the gap between the wires are locally expanded, the gap between the first and the second wires in the first regions is preferably 1.2 times or more and 2.0 times or less as wide as the gap between the first and the second wires in the second regions. Thereby, it becomes possible to make the aspect ratio of expanded regions as desired.
In the case that the gap between the wires is locally contracted, the gap between the first and the second wires in the second regions is preferably 10% or more and 50% or less of the gap between the first and the second wires in the first regions. Thereby, the second regions can be filled with the nitride film.
A semiconductor device according to yet another aspect of the present invention comprises a semiconductor substrate having a main surface, wires formed on the main surface with an insulation film interposed, a hard mask film on the wires, a first nitride film covering the side walls of the hard mask film and the wires, a second nitride film covering the first nitride film and extending on the main surface, an interlayer insulation film covering the second nitride film and plug parts formed within the interlayer insulation film.
By forming the second nitride film as a substrate protective film in this way, it becomes possible to carry out a wet reflow process to the interlayer insulation film. Thereby, the filling in characteristics of the interlayer insulation film can be improved so that the defective fillings of the interlayer insulation film between the wires can be controlled.
The above described interlayer insulation film has contact holes which reach the main surface and the plug parts are formed within the contact holes. In this case it is preferable to form a silicide layer on the main surface located directly below the plug parts. Thereby, the contact resistance between the plug parts and the semiconductor substrate can be reduced.
The semiconductor device is provided with an oxide film between the second nitride film and the main surface and the interlayer insulation film has contact holes reaching the main surface so that the plug parts are formed within the contact holes. The edge parts of the second nitride film project toward the inside of the contact holes. In this case it is preferable for parts of the plug parts to extend under the projecting parts of the second nitride film. Thereby, the contact areas between the plug parts and the semiconductor substrate can be increased and the contact resistance between the plug parts and the semiconductor substrate can be reduced.
A production method for a semiconductor device according to one aspect of the present invention comprises the following steps. Wires and a hard mask film are formed on the main surface of a semiconductor substrate with an insulation film interposed. A nitride film is formed so as to cover the hard mask film. The upper edge corner parts of the nitride film are rounded. An interlayer insulation film is formed so as to cover the nitride film. Plug parts are formed within the interlayer insulation film.
By rounding the above edge corner parts of the nitride film in this way, defective fillings of the interlayer insulation film between the wires can be limited as described above.
A plurality of wires are preferably formed and the step of rounding the upper edge corner parts of the nitride film preferably includes a step of etching the upper edge corner parts of the nitride film under the condition where a resist is left in between the wires. Thereby, the upper edge corner parts of the nitride film can be rounded while protecting the nitride film located between the wires.
A production method for a semiconductor device according to another aspect of the present invention comprises the following steps. Wires and a hard mask film are formed on the main surface of a semiconductor substrate with an insulation film interposed. The upper edge corner parts of the hard mask film are rounded. A nitride film is formed so as to cover the hard mask film. An interlayer insulation film is formed so as to cover the nitride film. Plug parts are formed within the interlayer insulation film.
In the case that the upper edge corner parts of the hard mask film are rounded, the upper edge corner parts of the nitride film can be rounded so that the defective fillings of the interlayer insulation film between the wires can be limited as described above.
A plurality of wires are performed and the step of rounding the upper edge corner parts of the hard mask film preferably includes the step of etching the upper edge corner parts of the hard mask film under the condition that a resist is left in between the wires. Thereby, when the upper edge corner parts of the hard mask film are rounded the side walls of the wires can be protected by the resist.
A production method for a semiconductor device according to still another aspect of the present invention comprises the following steps. Wires, including a silicon film and a silicide film, as well as a hard mask film are formed on the main surface of a semiconductor substrate with an insulation film interposed. The sides of the silicide film are shifted to the inner side of the wires from the sides of the silicon film. An oxide film is formed on the side walls of the wires. A nitride film is formed so as to cover the hard mask film and the oxide film. An interlayer insulation film is formed so as to cover the nitride film. Plug parts are formed within the interlayer insulation film.
By shifting the sides of the silicide film toward the inside of the wires than the sides of the silicon film in this way, the oxide film can be prevented from projecting to the side after the oxide film is formed on the side walls of the wires. Thereby, the defective fillings of the interlayer insulation film between the wires can be limited.
A production method for a semiconductor device according to yet another aspect of the present invention comprises the following steps. Wires and a hard mask film are formed on the main surface of a semiconductor substrate with the first insulation film interposed. The second insulation film is formed so as to cover the hard mask film. The second insulation film is etched and a side wall insulation film is formed so as to extend from the side walls of the wires to the side walls of the hard mask film. A nitride film is formed so as to cover the side wall insulation film. An interlayer insulation film is formed so as to cover the nitride film. Plug parts are formed within the interlayer insulation film.
By forming a side wall insulation film as described above, the side walls in the regions located between the wires can be sloped gently so that the defective fillings of the interlayer insulation film between the wires can be limited.
A production method for a semiconductor device according to still yet another aspect of the present invention comprises the following steps. Wires and a hard mask film are formed on the main surface of a semiconductor substrate with the first insulation film interposed. A nitride film is formed so as to cover the hard mask film. An interlayer insulation film is formed so as to cover the nitride film. Contact holes are formed in the interlayer insulation film. The second insulation film is formed so as to cover the side walls of the contact holes. Plug parts are formed in the regions surrounded by the second isolation film.
By forming an insulation film covering the side walls of the contact holes in this way, even in the case that a conductive material infiltrates into the interlayer insulation film, short circuiting between this conductive material and a plug part can be prevented without fail.
A production method for a semiconductor device according to still another aspect of the present invention comprises the following steps. Wires and a hard mask film are formed on the main surface of a semiconductor substrate with an insulation film interposed. The first nitride film is formed so as to cover the hard mask film. The first nitride film is etched and a side wall insulation film is formed on the side walls of the wires and the hard mask film. The second nitride film is formed so as to extend on the main surface while covering the side wall insulation film. An interlayer insulation film is formed so as to cover the second nitride film. Plug parts are formed within the interlayer insulation film.
By forming an interlayer insulation film under the condition that the second nitride film is formed on the main surface of the semiconductor substrate in this way, a wet reflow process can be carried out on the interlayer insulation film so that the filling in characteristics of the interlayer insulation film can be increased between the wires.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.